Willow Jarosh and Stephanie Clarke are registered dietitians and founders of C&J Nutrition. We consulted them to see if certain foods or beverages prevent calcium absorption and what you need to know to fulfill your daily dose.
FitSugar: Can food or beverages block calcium absorption, and why does this occur?
C&J Nutrition: Yes, certain foods/beverages can inhibit calcium absorption. Foods that contain oxalate can reduce the amount of calcium you absorb because the oxalate binds with calcium in your intestines. So, not as much calcium can be absorbed from your intestines and therefore passes right through you.
FS: Which foods block calcium absorption?
C&J: Foods that contain oxalates are rhubarb, beets, okra, spinach, Swiss chard, sweet potatoes, tea, chocolate, and soy products. Foods rich in phytates can also block absorption, and they include fiber-containing whole-grain products and wheat bran, beans, seeds, nuts, and soy isolates. But, it's not recommended that people stop eating these foods. As long as you eat a varied diet and get adequate calcium intake each day, the small amount of calcium absorption inhibition from phytates or oxalates shouldn't be a problem. In fact, the small amount of inhibition from these foods is even accounted for in the dietary reference intakes! Alcohol intake can reduce calcium absorption, but the amount of alcohol it would take to create an effect on calcium status isn't known.
FS: Which does the body absorb better: calcium from food or calcium from supplements?
C&J : Either. But keep in mind that our bodies can only absorb around 500-600mg of calcium at a time, so don't take your calcium supplement with a glass of milk. Bottom line: Don't avoid foods that contain oxalates or phytates, but be sure to get the recommended amount of calcium each day (1000mg for women between 19-50 years of age), and eat a daily variety of fruits, veggies, whole grains, beans, lean protein, and healthy fats.